Molecular Homology

The NCSE asserts that Explore Evolution‘s discussion of the universal genetic code, its variants, and puzzles ab The NCSE asserts that Explore Evolution‘s discussion of the universal genetic code, its variants, and puzzles about the origin of the variant codes, “is based on misunderstanding and/or misrepresentation of the available knowledge and of the scientific record.” The NCSE’s own discussion of this area, however, is very deeply confused. The NCSE does not grasp basic facts about the variant code puzzle, and this leads to several serious errors in their discussion. 1. Making a hash of a fascinating puzzle — the NCSE discussion We begin with the NCSE’s most serious error. They write: First, contrary to the key assertion [of EE], scientists have been aware of Read More ›

The National Center for Science Education critique of Explore Evolution argues that molecular data confirm the theory of common ancestry. This might be the case, if it were possible to show how molecular data could also disconfirm the theory of common ancestry. But here, as elsewhere in their rebuttal, the NCSE presupposes common ancestry as a first principle. Molecular data should fit to a monophyletic tree. In this respect, of course, the NCSE rebuttal reflects widespread reasoning, and actual practice, within evolutionary biology and systematics. Start with the geometry (or topology) of a tree, and locate the data on that geometry. As Sober and Steel (2002, 395) note, This proposition [of common ancestry] is central because it is presupposed so widely in Read More ›

One theme of Explore Evolution (EE) addresses differing views among evolutionary biologists about Darwin’s Tree of Life, i.e., the theory of the universal common ancestry of all organisms on Earth: more precisely, the monophyly of terrestrial life, rooted in the Last Universal Common Ancestor, or LUCA. While the majority position within evolutionary biology endorses monophyly, a growing minority of workers argue for multiple independent origins, or polyphyly (see below). It’s an important controversy, well worth the attention of textbooks. But John Timmer accuses EE of a “bait-and-switch” move in describing this controversy. By “lumping…together in a single footnote” several scientists with very different views about the overall pattern of life’s history, he argues, EE tries for “borrowed credibility,” misleading its readers about the true outlines of Read More ›